Use access() instead of fopen() to search for PCH

Use access() instead of fopen() to search for PCH

Since all we want to do is find out whether the file exists and can be
read, use the appropriate function.

Signed-off-by: Simon Richter <Simon.Richter@hogyros.de>
Reviewed-by: He Junyan <junyan.he@inbox.com>
Reviewed-by: Zhigang Gong <zhigang.gong@linux.intel.com>